Support tweaked Taproot FROST deposit sweeps

[mswilkison]

Stacked on feat/frost-schnorr-migration-scaffold.

Adds Taproot tweak helpers and per-input merkle-root metadata for tweaked P2TR key-path inputs, routes wallet signing through root-aware FROST/tbtc-signer requests, and verifies native aggregates against the tweaked output key.

Also adds Taproot-native, refund-preserving deposit sweep support: Bridge/WalletProposalValidator bindings for TaprootDepositRevealed and validateTaprootDepositSweepProposal, Taproot refund script and merkle-root derivation, proposal generation that separates legacy and Taproot deposits, Taproot sweep assembly with per-input merkle roots, P2TR wallet main UTXO/change outputs, and Electrum script-based P2TR wallet UTXO discovery.

Verification: go test ./pkg/bitcoin ./pkg/tbtc ./pkg/tbtcpg ./pkg/chain/ethereum; go test ./pkg/...; go test -tags frost_native ./pkg/frost/signing ./pkg/tbtc -run 'TestMessageDigestFromBigInt|TestBuildTaggedLegacyCompatibleNativeExecutionFFISigningPrimitive_Sign_NativeFROSTPath|TestExecuteBuildTaggedTBTCSignerBootstrapCoarseRound|TestWalletTransactionExecutor_SignTransaction|TestSigningExecutor'; go test -tags 'frost_native frost_tbtc_signer cgo' ./pkg/frost/signing.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: b68742b0-1090-4223-b624-397364b7decd

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/tweaked-taproot-deposit-sweeps

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}